The number of protons present in the nucleus of an atom is referred to as atomic number (Z). In a neutral atom, the number of protons is equal to the total number of electrons present in the atom. The mass number (A) of an atom is the total number of protons and neutrons, i.e. total number of nucleons. Protons and neutrons are present in the nucleus. The composition of an atom can be written as subscript and superscript on the left-hand side of the element symbol. Atomic number (Z) is written as the subscript and mass number (A) is written as the superscript, i.e. ZAX. Isotopes have the same atomic number but different mass numbers.
1. Which of the following statements is correct regarding sodium atoms? (Z = 11, A = 23)
(a) It has 11 protons, 12 electrons, and 11 neutrons.
(b) It has 11 protons, 11 electrons, and 11 neutrons.
(c) It has 11 protons, 12 electrons, and 12 neutrons.
(d) It has 11 protons, 11 electrons, and 12 neutrons.
2. Which of the following determines the identity of a chemical element?
(a) The number of neutrons
(b) The number of protons
(c) The sum of the number of protons and neutrons
(d) The number of electrons
3. Which of the following particles is positively charged in an atom?
(a) Protons
(b) Neutrons
(c) Electrons
(d) Both (a) and (b)
4. Isotopes of a neutral atom have
(a) an equal number of neutrons
(b) a different number of protons
(c) the same mass numbers
(d) the same number of electrons
5. What is the number of protons in an element with atomic number 17 and mass number 37?
(a) 17
(b) 20
(c) 22
(d) 21
6. Deuterium is an isotope of a hydrogen atom. It contains
(a) one neutron and two protons
(b) no neutrons and one proton
(c) one proton and one neutron
(d) one electron and two neutron
7. Find the number of neutrons in a Zn2+ ion. The mass number is 70.
(a) 40
(b) 36
(c) 38
(d) 34
8. The number of electrons in a neutral atom represents its
(a) atomic number
(b) atomic mass
(c) mass number
(d) number of nucleons
9. Elements having the same atomic number but different mass numbers are called
(a) isotones
(b) isotopes
(c) isobars
(d) none of the above
10. Which of the following contribute mainly to the mass of an atom?
(a) Neutron and electron
(b) Proton and electron
(c) Neutron and proton
(d) None of the above
Answer
|
1. (d) |
2. (b) |
3. (a) |
4. (d) |
5. (a) |
|
6. (c) |
7. (a) |
8. (a) |
9. (b) |
10. (c) |
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